Today it’s my Maglite XL50 led flashlight. Makes my stylus light up when I’m looking thru my loupe.
On it’s brightest setting, it can probably be seen by the space station.
I often use the pocket rule when I am making cables and power cords. Handy for ensuring the length of shrink tube or the amount of jacket I am taking off the cable ends.
Decibel meters, even some of the free ones available in appstore, are so useful for audio tasks: equalizing volumes for head-to-head AB shootouts, becoming familiar with the decibel levels of everyday sounds, proving to your wife that you are not damaging your hearing at the volumes you listen to, …
I’m sure the dedicated ones work much better, but even the freebies are useful …
Oh yeah and ear plugs when I’m mowing so that I’ll hopefully still be able to hear when I get old
The reason I went for x-protectors are the booties that can put on or taken off depending on the surface. On for hardwood, off for carpet. I love these things. Whenever I need to move my amp (the Pass or BHK250, both pushing 85 lbs), I slip these under it with the booties on to slide it across my wood floor. I’ve also used them in the past for rough speaker placement.
Makes my audiophile life a whole lot easier.